Tobacco sheet manufacture of high wet strength



United States Patent O US. Cl. 131140 2 Claims ABSTRACT OF THEDISCLOSURE This invention relates to the manufacture of coherent tobaccoproducts suitable for smoking and more particularly to such tobaccoproducts in the form of a leaf or foil with an appearance and otherphysical qualities that they may be applied as the outer wrapper ofcigars, cigarillos and the like in lieu of leaf tobacco ordinarily usedas such wrapper. A feature of the new tobacco products is highresistance to disintegration when moistened and even chewed.

In essence, tobacco products of high wet strength are made of comminutedtobacco and film-forming cellulose derivatives which are substantiallyinsoluble in water at normal (25 C.) and higher temperatures but aresubstantially soluble in organic acid of not less than about by weightconcentration in water. Preferably, the water-insoluble cellulosederivative is dissolved in formic or acetic acid of about to by weightconcentration in water. While a tobacco sheet produced simply byadmixing dry-ground tobacco powder with a solution of a cellulosederivative in acetic acid, casting and drying the resultant tobaccosuspension will have high wet strength, such tobacco sheet will not haveadequate resistance to chewing particularly when used as wrapper onlarge cigars that are frequently subjected to excessive chewing by somesmokers. However, where chew resistance in addition to wet strength isdesired in a tobacco sheet, this is achieved pursuant to the inventionby incorporating in the suspension of tobacco in acetic acid highlyhydrated, well-beaten cellulose fibers which may be derived fromtobacco, particularly tobacco stems, or other plants as is known in thepulp art.

The particularly valuable tobacco sheets which include cellulose fibersfor chew resistance have been made possible by the dual nature of thesolvent used in accordance with this invention which combines organicacid to dissolve the water-insoluble cellulose derivative with water tohydrate the cellulose fibers.

BACKGROUND OF INVENTION This is a division of application Ser. No.598,215, filed Dec. 1, 1966, now Patent No. 3,416,537.

There has long been a need for tobacco sheets of high wet strength andgood chew resistance, particularly for use as wrappers on cigars.Numerous proposals have been made but none has been completelysatisfactory.

Detert et al. first disclosed in US. Patent 2,893,400 a tobacco sheetfor use as cigar wrapper made from finely pulverized tobacco andrnethylcellulose dissolved in an anhydrous solvent consisting of amixture of methanol and methylene chloride. However, these patenteesadmitted the low wet strength of their tobacco sheet in US. Patent2,927,588 wherein they proposed the addition of phosphoric acid to themixture of finely pulverized tobacco and an anhydrous solution ofrnethylcellulose. The addition of phosphoric acid was alleged to havethe surprising result that the resistance of the tobacco foils 3,496,947Patented Feb. 24, 1970 to tearing, their resistance to 'water, and theirstability in storage are improved to such an extent that they can bemanipulated without difficulty either by hand or by machines,interestingly enough, the patentees still did not allege that theirtobacco sheet had any chew resistance and they failed to take intoaccount that phosphoric acid is known to be a combustion retardant.

In still another effort to find a satisfactory process,

-Detert et al. later suggested in US. Patent 3,062,688 that finelypulverized tobacco be mixed with a solution of a combination ofwater-soluble rnethylcellulose and a waterinsoluble cellulose derivativein an organic solvent consisting of a mixture of methylene chloride andmethyl alcohol. The tobacco foil thus produced was alleged by thepatentees to overcome the disadvantages of their prior foils which, inthe words of the patentees, do not meet the high requirements of coverleaves for cigars and cigarillos with respect to their resistance totearing and to saliva, and also because they have not sufiicientsuppleness. However, even this latest proposal of Detert et al. fails toproduce a tobacco sheet of sufficiently high wet strength and chewresistance to be acceptable as wrapper on cigars that are subjected towet-chewing by many "smokers.

Another approach to the same problem, has been the concept of producingtobacco sheets with water-soluble binding or film-forming agentstogether with cross-linking agents which are intended to render theresultant tobacco sheet water-insoluble. Thus, it was proposed in closedthe use of dialdlhyde starch as cross-linking agent be cross-linked byglyoxal. US. Patent 2,887,414 disclosed the use of dialdahyde starch ascross-linking agent for a water-soluble binding agent, while US. Patent3,-

106,212 suggested the use of moisture resistance agents DESCRIPTION OFINVENTION Fundamental to the invention is the selection of an aqueoussolution of organic acid as the solvent for cellulose derivatives whichare known to be binding agents or film-formers but which aresubstantially insoluble in water at normal (25 C.) or highertemperatures. The organic acid must be completely miscible with waterand volatile at temperatures which may be used to dry the tobaccoproduct without substantial impairment of its smoking quality. Formicand acetic acids best fulfill these requirements of the organic acidused as solvent. Acetic acid is preferred particularly inasmuch as it isless expensive than formic acid. While aqueous organic acid with as lowas 15% by weight concentration and as high as concentration may serve assolvent, the preferred solvent is generally in the range of about 20% to40% by weight of formic or acetic acid in water.

The water-insoluble cellulose derivative chosen for the production of atobacco sheet or other coherent form must be soluble at normaltemperature in the aqueous organic acid used as solvent. Since thepreferred solvent is aqueous formic or acetice acid in the range ofabout 20% to 40% by weight concentration, the preferred water-insolublecellulose derivatives are those which are substantially soluble in suchsolvent even though water-insoluble cellulose derivatives requiringaqueous formic or acetic acid ofas high as about 80% by weightconcentration may be used pursuant to this invention. It is well to notethat generally the dissolving of the water-insoluble cellulosederivative is preferably carried out by initially using an organic acidof higher concentration than is ultimately desired for the production ofa tobacco sheet or other coherent form of tobacco, and then adding waterto the solution to bring the concentration of the organic acid to thedesired value. Many of the water-insoluble cellulose derivatives usefulpursuant to this invention require this dissolving procedure becausethey are not adequately dissolved by direct suspension, say, in aqueousacetic acid of about to 40% by weight concentration but they remainsubstantially in solution when their solutions in glacial acetic acid orin concentrated acetic acid, e.g., about 80% by weight concentration,are diluted with water to acetic acid solutions of about 20% to 40% byweight acid concentration.

The organic acid used as solvent pursuant to this invention may be notonly a mixture of formic and acetic acids but also a mixture of eitheror both of these acids with a somewhat less volatile acid likeproprionic acid or even a substantially non-volatile acid like lactic orcitric acid. Poorly volatile and non-volatile acids are used as only theminor component in admixtures with formic or acetic acid. The use of aminor proportion of a nonvolatile acid such as malic or tartaric acid aswell as lactic or citric acid serves the duel purpose of acting as partof the organic acid solvent for the water-insoluble cellulose derivativeand of plasticizing the tobacco product to render it more flexible andworkable in making cigars especially when the product is a tobacco sheetapplied as cigar wrapper. Generally, such acids that remain in a tobaccoproduct made pursuant to this invention are used in an amount notexceeding about 20% by weight based on the tobacco content of theproduct. Even at such a comparatively high level of acid in the tobaccoproduct. hydroxylated polycarboxylic acids in particular have been foundto be not objectionable during the smoking of the tobacco product.

Dry-ground or pulverized tobacco may be formed into a coherent formhaving appreciable wet strength with the aid of a water-insolublecellulose derivative dissolved in aqueous formic or acetic acid. In suchcase where no fiber is present in formulating the tobacco product, theuse of a minor amount of plasticizing acid such as citric or lactic aspart of the aqueous organic acid is generally advisable inasmuch as theplasticizing acid tends to prevent cracking especially when the productis a tobacco sheet. However, considerably higher wet strength may beobtained by incorporating in the formed tobacco product highly hydrated,well-beaten cellulose fibers. The pulp of refined cellulose fibers maybe prepared from tobacco, particularly stems, or from the usual sourcesused in the pulp industry. In terms of the improved physical properties,especially tensile strength, of a tobacco sheet achieved byincorporating a certain weight percentage of refined fibers of thesulfite or sulfate type pulp, generally at least twice as much refinedfibers derived from tobacco stems are required for the same improvedproperties.

The selection of the water-insoluble cellulose derivative to be used asbinding agent is based not only on its solubility in aqueous organicacid, especially acetic acid, but also on its viscosity when sodissolved. A water-soluble cellulose derivative like methylcellulose maybe made water-insoluble by increasing the degree of substitution ofhydroxyl hydrogen in the original cellulose molecular chain withhydrophobic substituents like methyl, ethyl and acetyl. However, it isknown that the cellulose molecular chain tends to degrade or break intoshorter chains as the degree of substitution is increased. Since thebinding or film-forming capacity of cellulose derivatives in tobaccosheets and other coherent bodies generally decreases as the cellulosemolecular chains become shorter, it is important for the purposes ofthis invention to select cellulose derivatives in which the degree ofsubstitution has been increased just enough to make the cellulosederivative substantially water-insoluble without degrading the molecularchains to an extent that the binding capacity of the cellulosederivative has been seriously impaired.

The length of cellulose molecular chains, commonly referred to as degreeof polymerization, is frequently determined by the viscosity of thecellulose derivatives in a given solvent, at a given concentration andat a given temperature. Thus, the degree of polymerization or vrscositygrade of a Water-soluble cellulose derivative like methylcellulose isusually established by the viscosity 1n centipoises (cps) at atemperature of 20 C. for a water solution containing 2% by weight of thecellulose derivative. For the water-insoluble cellulose derivatives usedin accordance with this invention, it has been found desirable todetermine the degree of polymerization, hereinafter called the acidviscosity grade, by measuring 1n a Brookfield R.V.T. viscosimeter (speed20 revolutions per minute) the viscosity at a temperature of 25 C. of 1%by weight of the cellulose derivative dissolved in aqueous acetic acidhaving an acetic acid content of by weight. Generally, the waterinsoluble cellulose derivative used pursuant to this invention isdesirably one having an acid viscosity grade of at least about cps. andpreferably at least about 250 cps.

Water-insoluble cellulose derivatives suitable for the purposes of thisinvention include water-insoluble grades of methylcellulose,ethylmethylcellulose, ethylcellulose, ethylhydroxyethylcellulose andcellulose acetate. Another group of suitable binding agents compriseswater-soluble grades of cellulose derivatives such as methylcellulose,hydroxyethylcellulose, methylhydroxyethylcellulose,ethylhydroxyethylcellulose, methylhydroxypropylcellulose andmethylhydroxybutylcellulose which have been acetylated to the extent ofrendering the cellulose derivatives substantially insoluble in water atnormal and higher temperatures. For example, water-solublemethylcellulose of 8000 cps. viscosity grade (2%.by weight in water at atemperature of 20 C.) and having a methoxyl content of about 30% byweight that has been acetylated to the extent that the cellulosederivative has an acetyl content of between about 5% and 12% by weighthas been found to be substantially water-insoluble but soluble inaqueous acetic acid of about 20% to 40% by weight concentration.

It should be noted that the water-insoluble cellulose derivatives usefulfor the purposes of this invention embrace not only the commerciallyavailable types that are soluble in the conventional organic solventssuch as a mixture of methylene chloride and methanol but also speciallyprepared types that are generally considered unsatisfactory for solutionin such conventional organic solvents. For instance, commerciallyavailable ethylcellulose has an ethoxyl content of over about 44% byweight and cellulose acetate has an acetyl content of over about 37% byweight; such cellulose derivatives are soluble in aqueous formic oracetic acid of about 80% by weight concentration. On the other hand,ethylcellulose and cellulose acetate made with, respectively, lowerethoxyl and acetyl contents (but not low enough to make these cellulosederivatives substantially soluble in water) are soluble in lessconcentrated aqueous formic or acetic acid with an acid content goingdown to about 15 by weight.

The specially made cellulose derivatives in contrast to the types whichare commercially produced for solution in conventional organic solventsoffer the advantages of obviating the use both of such highlyconcentrated organic acid as aqueous acetic acid of 80% by weightconcentration and of the comparatively larger proportion of highlyhydrated, refined cellulose fibers required to prevent cracking of atobacco sheet during its manufacture with a cellulose derivative of thetype "offered commercially for solution in conventional organicsolvents. Moreover, a tobacco sheet made with the latter type ofcellulose derivative is usually not sufficiently plasticized by water tomake it stretchable enough for use as wrapper on cigars of the perfectoor like shapes; in such case, a water-soluble or highlywater-susceptible binding agent is desirably used together with thecellulose derivative so that the resulting tobacco sheet can beplasticized by water to give it the desired degree of stretch orelasticity.

While humectants and plasticizers such as glycerol, sorbitol and variousglycols are generally used in tobacco smoking products to avoidexcessive drying and embrittlement, it is noteworthy that tobacco sheetsand other coherent bodies of tobacco produced in accordance with thisinvention rarely require the use of humectants or plasticizers becausewater alone is an adequate plasticizer. It has been known that tobaccosheets with a high moisture content, usually over 20% by weight, areduring prolonged storage susceptible to deterioration in one form oranother such as loss of strength, change of appearance or even moldformation. By contrast, the tobacco sheets of this invention may be madewith a comparatively low moisture content, say about 20% by weight, soas to have good stability during prolonged storage. While such tobaccosheets will have poor elasticity, this physical limitation is easilycorrected at the time such tobacco sheets are being utilized in themanufacture of a smoking product, such as wrapper on cigars, bymoistening with water. The tobacco sheets of the invention may bemoistened by a water spray, by contacting a wet roller or even bydipping. The moistening of the tobacco sheets with water is desirablycontrolled so that the moisture content then generally is in the rangeof about 35% to 45% by weight inasmuch as such moistened tobacco sheetshave the necessary stretch and other physical properties to besuccessfully applied as wrappers on cigars of even intricate shapes.Obviously, the amount of water added to a tobacco sheet need not be morethan that just required to make the workability of the tobacco sheetsatisfactory for its intended use such as wrapper on cigars.

When a tobacco sheet is to be applied as the outer covering or wrapperof a cigar, the addition of an ash-whitening material like titaniumdioxide and an ash-strengthening agent like comminuted ceramic fiber tothe basic components of the tobacco sheet may be advisable.

The coherent tobacco products of this invention may be used incigarettes, pipe tobacco and like smoking products but the high wetstrength and chew resistance that may be achieved in tobacco sheets madeby this invention clearly indicate that such tobacco sheets areespecially attractive for use as wrappers on cigars. Hence, furtherelaboration of the invention will be made in terms of its most valuablecommercial application, namely, tobacco sheets used as wrappers oncigars.

For a better understanding of the invention and its scope, illustrativeembodiments are presented hereinbelow in detail. In the examples,proportions are given in parts and percentages by weight unlessotherwise specified.

EXAMPLE 1 Burley tobacco stems cut to pieces of about 1 inch in lengthwere admixed with water to form a 7.4% suspension which was placed in asealed autoclave for treatment in accordance with the process of U.S.Patent 3,- 076,729 to Garbo. Approximately 25% of the volumetriccapacity of the autoclave was charged with commercially pure oxygen atan initial pressure of 700 p.s.i.g. (pounds per square inch gauge).While stirring, the stem suspension was heated until a temperature ofabout 300 F. was reached and then this temperature was maintained for a20-minute period during which the pressure was held at about 1200p.s.i.g. with the help of added oxygen when needed. Thereupon, thesuspension in the autoclave was rapidly cooled to a temperature of about175 F. and discharged at a pressure of about 50 p.s.i.g. through a Rietzdisintegrator fitted with a screen having %2-lnCh openings.

The thus treated suspension was filtered to discard the liquid and theresidual stem material was so washed on the filter that the dry solidsof the washed stem material had a ratio of total solids towater-insoluble solids, hereinafter called the wash ratio, of 1.2. Thewashed stern material was again dispersed in water to form a 6%suspension based on the dry solids of the washed stem material and thissuspension with added titanium dioxide was repeatedly passed through adisc refiner until the refined stem fiber had a reverse freeness of 70as determined by the Schopper-Riegler type beating and free ness tester.The titanium dioxide which was added to the stem suspension in the ratioof 1 part to 12.5 parts of dry solids in the suspension served twopurposes, namely, lightening the color of the finished tobacco sheet andyielding a whitish ash when the tobacco sheet was smoked as wrapper on acigar.

The refined pulp of Burley stems was admixed with water-insolublemethylcellulose (39.5% methoxyl content) having an acid viscosity gradeof 310 cps. that had been dissolved in aqueous acetic acid and wasfurther admixed with a dry-ground blend of cigar-type tobaccos basedprincipally on Wisconsin tobacco. The pulverized tobacco blend passedthrough -mesh screen (U.S. Sieve size) but only 85% passed throughZOO-mesh screen. To strengthen the ash of the tobacco sheet, a ceramicfiber (Fiberfrax sold by The Carborundum Company), which was cut to veryshort fragments while suspended in water by a high-speed, high-shearstirrer, was also added to the pulp of Burley stems. The proportioningof the admixed components was such that the final slurry contained:

Parts Pulverized tobacco blend 150 Refined Burley stems (dry solids)Water-insoluble methylcellulose 40 Titanium dioxide 10 Ceramic fiber 3all in 20% aqueous acetic acid at a total concentration of 5.9% of theaqueous acetic acid. The final slurry had a viscosity of 7000 cps. at atemperature of 10 C.

This slurry was spread evenly on a stainless steel belt which wassubsequently heated first with hot air impingement on the slurry-coatedbelt and as soon as enough water and acetic acid had been removed byevaporation to set the slurry coating on the belt was further heatedwith steam condensation on the underside of the steel belt. The driedcoating on the belt was rehumidified to a moisture content of about 35%and stripped from the belt as a tobacco sheet. The moisture content wasdecreased to about 20% with the aid of infra-red lamps and the tobaccosheet approximately 0.002 inch thick was then wound up in rolls suitablefor use on a cigar-making machine.

The tobacco sheet had a pleasing appearance and a brown color similar tothat of some grades of cigar wrapper leaf tobacco. The Finch tensilestrength of this tobacco sheet, determined according to ASTM standardtest B82948, using an immersion time of 30 seconds in water and a testsample of double width, was 125 g./rnm. (grams per square millimeter).

Perfecto-shape cigar bunches were wrapped with this tobacco sheet afterincreasing its moisture content to about 45% since at this high moisturecontent the tobacco sheet had good stretch so that it could be pulledover the curved portions of the perfecto-shape cigar bunches and thusconform to the shape without forming gaps or creases in the wrappersheet. At the time of application of the tobacco sheet as cigar wrapper,an odor of acetic acid was noticed because of the volatilization of asmall residue of acetic acid in the tobacco sheet as stripped from thestainless steel belt. However, after the finished cigars were dried toan average moisture content of about 13%, the odor of acetic acid hadvanished.

The prefecto-shape cigars with the tobacco sheet wrapper were found toburn with an attractive whitish, firm ash and to have a very agreeablesmoke taste. Smokers who are accustomed to chewing a cigar while smokingit noted that this tobacco sheet wrapper withstood chewing better thanmost tobacco leaf wrappers.

EXAMPLE 2 Burley tobacco stems processed as in Example 1 but refined toa reverse freeness of 92 were passed from the disc refiner once througha valve-type homogenizer at a pressure of 4500 p.s.i.g. Only 1 part oftitanium dioxide was added to 100 parts of dry solids in the tobaccostem suspension prior to refining this suspension.

Ethylcellulose of 35.5% ethoxyl content was dissolved in aqueous aceticacid of 70% by weight concentration and was admixed with a dry-groundblend of 50% Sumatra and 50% Santo Domingo tobaccos, all passing through100-mesh screen. The components were admixed to give a final slurrycontaining:

Parts Pulverized tobacco blend 150 Refined Burley stems (dry solids) 100Ethylcellulose 50 Titanium dioxide 1 all in 45% aqueous acetic acid at atotal concentration of 6% of the aqueous acetic acid.

This slurry was converted into a tobacco sheet as described inExample 1. The appearance and physical properties of this tobacco sheetwere comparable to those of the tobacco sheet of Example 1.

Blunt-shape cigars were made with the tobacco sheet of this example aswrapper. The cigars had the typical appearance of moderate-priced cigarsand, in smoking tests, were found to have considerable chew-resistanceand a pleasing smoke taste.

EXAMPLE 3 The Burley stems of Example 1 were first passed through heatedrolls moving at differential speeds which flattened and tore the stempieces to yield a product in chip form, called flaked stems. The flakedstems were suspended in water, autoclaved and further processedincluding washing to a wash ratio of 1.1 as described in Example 1. Thewashed stern material with the added titanium dioxide was refined andhomogenized as described in Example 2.

The thus prepared Burley stems were dewatered to a solids content of 15%and added slowly with high agitation to a solution of a mixture of 37.5parts of methylcellulose (39% methoxyl content) and 12.5 parts ofethylcellulose (45% ethoxyl content) in glacial acetic acid until 100parts (dry solids basis) of the stem material had been added. Water wasthen added slowly under high agitation to bring the acetic acidconcentration to 80%. Finally, 100 parts of a blend of dry-groundWisconsin tobacco fines from cigar manufacture were added. The resultingslurry, having a solids content of 4.5% and a viscosity of 21,000 cps.at 20 C., was formed into a tobacco sheet as described in Example 1. Theproduct was light in color, resembling a desirable cigar wrapper, andhad properties suitable for conformance to shaped cigars.

EXAMPLE 4 The procedure in Example 3 was followed in all details exceptthat in place of 37.5 parts of the water-insoluble methylcellulose, 25parts of water-soluble methylcellulose (30% methoxyl content) of 1500cps. viscosity grade was used, while the quantity of the ethylcellulosewas doubled to 25 parts. The resulting tobacco sheet in appearance,physical properties and smoking qualities was very satisfactory was acigar wrapper.

EXAMPLE 5 Flaked Burley stems were processed as in Example 3 except thata conical refiner was used instead of the disc refiner. To a solution of50 parts of ethylmethylcellulose with a degree of substitution of 0.94ethyl and 1.34 methyl (acid viscosity grade of 110 cps.) in glacialacetic acid were added 100 parts (dry solids basis) of the refined andhomogenized Burley stem material. Sufficient water was added to bringthe acetic acid concentration to 30% and then 150 parts of dry-groundSumatra tobacco were admixed to yield a slurry containing 7.5% solids.After deaeration, the slurry had a viscosity of 12,800 cps. at atemperature of 11 C.

The slurry was converted to a tobacco sheet as described in Example 1.The resulting tobacco sheet had good cigar wrapper properties includingattractivve color and texture. Panatella-shape cigars made with thiswrapper sheet withstood considerable chewing during smoking tests inwhich the smoke taste was rated very good.

EXAMPLE 6 The processed Burley stems of Example 3 were added to theextent of 50 parts (dry solids basis) to a solution of 20 parts ofacetylated methylcellulose (prepared by acetylating water-solublemethylcellulose of 8000 cps. viscosity grade to 8% acetyl content) inglacial acetic acid. Sufficient water was added to bring the acetic acidconcentration to 35% and then 150 parts of dry-ground Java tobacco wereadmixed to yield a slurry with a solids content of 7% and a viscosity of6500 cps. at 30 C.

The tobacco sheet formed from this slurry as described in Example 1,having an unusually high tobacco content (91% dry basis), had a tensilestrength of 495 g./mm. and a Finch tensile strength of 75 g./mm. Itsperformance as a cigar wrapper was very satisfactory.

EXAMPLE 7 Cellulose fibers (fully bleached sulfate softwood pulp) weredispersed in water at a dry solids concentration of 3% and passedrepeatedly through a disc refiner until a Schopper-Riegler reversefreeness of 47 was attained. Eighty parts of acetylated methylcellulose(8.4% acetyl content, 28% methoxyl content, acid viscosity grade of 920cps.) were dissolved in 4940 parts of 70% aqueous acetic acid. Twentyparts of water-soluble methylcellulose (8000 cps. viscosity grade) weredissolved in the same acetic acid solution.

The refined cellulose fiber slurry was added to the extent of parts (drysolids basis) to the aqueous acetic acid solution of the cellulosederivatives under high agitation. Then 15 parts of titanium dioxide, 5parts of fragmented Fiberfrax and 800 parts of Connecticut shade wrappertobacco cuttings, which had been dry-ground so that 100% passed through100-mesh screen and passed through ZOO-mesh screen, were uniformlydispersed in the cellulose fiber slurry. The entire mixture was dilutedwith 3690 parts of water to bring the acetic acid concentration to 30%.The viscosity of the final mixture was 6600 cps. at a temperature of 21C.

The tobacco sheet produced from this final mixture as described inExample 1 was found to be adequate in all respects as a cigar wrapper.

EXAMPLE 8 Flaked Connecticut shade tobacco stems were suspended in waterat a concentration of 7.5% autoclaved, filtered, washed and refined asdescribed in Example 1. A 4% solution in 50% aqueous formic acid wasprepared of a mixture of acetylated methylcellulose (8.4% acetylcontent, 28% methoxyl content, acid viscosity grade of 360 cps.) andwater-insoluble methylcellulose having 40.3% methoxyl content (acidviscosity grade of 345 cps).

A slurry of refined cellulose fibers was prepared as described inExample 7. The processed Connecticut shade tobacco stem slurry and therefined cellulose fiber slurry were mixed together and added to theaqueous formic acid solution of the cellulose derivatives. To this mixedslurry, dry-ground Connecticut shade wrapper tobacco cuttings asdescribed in Example 7, Fiberfrax, and titaniurn dioxide were added. Thefinal slurry had 7% solids in aqueous formic acid of 40% concentrationand contained:

Parts Processed Connecticut shade tobacco stems (dry solids) 20.0Refined cellulose fibers (dry solids) 10.0 Ground Connecticut shadewrapper tobacco 55.0 Acetylated methylcellulose 3.0 Water-insolublemethylcellulose 9.5 Fiberfrax 0.75 Titanium dioxide 1.75

The final slurry was converted into a tobacco sheet having a dry weightof 35 g./m. (grams per square meter), a tensile strength of 870 g./mm.and a Finch tensile strength of 170 g./mm. Used as a cigar wrapper, theproduct had high chew resistance and pleasing smoking qualities.

EXAMPLE 9 To 1358 parts of a 6% solution of cellulose acetate (about 28%acetyl content) in aqueous acetic acid of about 40% acid content wereadded 2260 parts of glacial acetic acid. To this solution were added1250 parts of a 3.6% aqueous solution of water-soluble methylcellulosemethoxyl content) of 1500 cps. viscosity grade, parts of a 50% aqueousslurry of titanium dioxide, 7.5 parts of fragmented Fiberfrax, and 1462parts of water. Then 4000 parts of the aqueous slurry of refinedcellulose fibers prepared as described in Example 7 but diluted to a drysolids concentration of 2.5% were added. Finally, 750 parts of adry-ground mixture of Wisconsin tobacco and tobacco fines resulting fromcigar manufacture were thoroughly blended into the total slurry whichwas diluted with 2000 parts of water to adjust the acetic acidconcentration to 30% and the viscosity to 5500 cps. at a temperature of21 C.

The tobacco sheet made from this final slurry as described in Example 1had a dry weight of 37 g./'m. and a Finch tensile strength of 190 g./mm.This product had the desirable characteristics of good cigar wrapertobacco.

EXAMPLE 10 To 75 parts of acetylated hydroxyethylcellulose (degree ofsubstitution of 1.5 acetyl, molecular substitution of 1.1 hydroxyethyl)slurried in 750 parts of water were added under agitation to 1890 partsof glacial acetic acid, To the resulting solution were added 1000 partsof water, 4.5 parts of fragmented Fiberfrax, and 21 parts of a 50%aqueous slurry of titanium dioxide. Next, 1720 parts of the aqueousslurry of refined cellulose fibers prepared as described in Example 7but concentrated to a dry solids content of 3.5% and 450 parts ofdry-ground Connecticut shade wrapper tobacco as described in Example 7were blended with the solution of cellulose derivative. The total slurrywas diluted with 990 parts of water so that the final acetic acidconcentration was 30% and the viscosity of the slurry was 7000 cps. at20 C.

The tobacco sheet made from this slurry as described in Example 1 wasattractive in appearance and served as a cigar wrapper of good smoketaste and chew resistance.

EXAMPLE 11 A mixture of 3 parts of acetylated methylcellulose (9.3%acetyl content, 28% methoxyl content) and 9.5 parts of water-insolublemethylcellulose (39.5% methoxyl content) was suspended in 60 parts ofwater and under high agitation 303 parts of glacial acetic acid wereadded. To the resulting solution were added 10 parts (dry solids basis)of autoclaved, filtered, washed, and refined Connecticut shade tobaccostems as described in Example 1 and 55 parts of Connecticut shadewrapper tobacco ground so that 100% passed through IOO-mesh screen and60% passed thorugh ZOO-mesh screen together with 20 parts of Connecticutshade tobacco stems ground so that 100% passed through -mesh screen andpassed through ZOO-meshed snreen. To this mixture were added 1.75 partsof titanium dioxide and 0.75 part of comminuted Fiberfrax. Sufficientwater was added to the total mixture to bring the acetic acidconcentration to 30%, the solids content to 9% and the viscosity to11,400 cps. at a temperature of 75 C.

The tobacco sheet made from the final mixture had a pleasing color,conformed well to shaped cigars and was as chew resistant as wrappertobacco of good quality.

EXAMPLE l2 Flaked Burley stems were cooked as a 12.5% suspension inwater in a heated kettle with stirring for one hour at a temperature of120 F. This suspension was then passed through a Rietz disintegratorfitted with a screen having -inch openings, filtered and washed to awash ratio of 1.2. The fibrous stem mass was redispersed in water togive a 5% suspension which was refined by 29 passes through a discrefiner and then one pass through a valve-type homogenizer at a pressureof 4500 p.s.i.g.

The thus processed Burley stems were slowly added under high agitationto a solution of 40 parts of water-insoluble methylcellulose (39.5methoxyl content) in 1630 parts of 80% aqueous acetic acid until 150parts (dry solids basis) of the processed stems were incorporated. Then150 parts of dry-ground Pennsylvania tobacco stems passed throughZOO-mesh screen) and 3 parts of fragmented Fiberfrax were added underhigh agitation. The mixture was slowly diluted under high agitation withwater to reduce the acetic acid concentration to 30%. The final slurryhad a solids content of 6.8% and a viscosity of 16,000 cps. at 11 C.

Tobacco sheet produced fro-m the final slurry as described in Example 1had a good light-brown color and performed satisfactorily in allrespects as a cigar wrapper.

EXAMPLE l3 Flaked Connecticut shade tobacco stems were processed asdescribed in Example 8. The resulting stern slurry was cooled to atemperature of 50 F. and added slowly with high agitation to a solutionof 3 parts of acetylated methylcellulose (5% acetyl content, 29%methoxyl content, acid viscosity grade of 560 cps.) in 400 parts ofglacial acetic acid until 97 parts (dry solids basis) of refined sternfibers were admixed.

The final slurry in aqueous acetic acid of 25% acid content was cast asa thin coating on a stainless steel belt with a doctor blade and thecoating was evaporated to dryness as the belt traveled over steam pandryers. The resulting dry tobacco sheet was rehumidified, stripped fromthe belt and rolled up as described in Example 1.

This tobacco sheet contained, on a dry basis, only 3% of cellulosederivative but had physical properties adequate for its use as achew-resistant cigar wrapper.

EXAMPLE 14 Seventy-five parts of dry-ground Connecticut shade wrappertobacco cuttings (100% passed through IOU-mesh screen and 85% passedthrough ZOO-mesh screen) were dispersed in 900 parts of a solutioncontaining 25 parts of acetylated hydroxyethylcellulose (degree ofsubstitution of 1.5 acetyl, molecular substitution of 1.1 hydroxyethyl)in aqueous acetic acid of 40% acid content.

Tobacco sheet with a dry weight of 40 g./m. was produced from theresulting slurry as described in Example 1. This tobacco sheet had aFinch tensile strength of about g./-mm. and good elasticity at amoisture content of 40%; it was a very acceptable wrapper onpanatella-shape cigars.

EXAMPLE 15 Seventy-five parts of the tobacco powder described in Example14 were dispersed in 900 parts of a solution containing 25 parts ofacetylated methylcellulose (10.1%

acetyl content, 28% methoxyl content, acid viscosity grade of 70 cps.)in a mixture of methylene chloride and methanol in which the weightratio of the two solvents was 9:1, respectively.

Tobacco sheet with a dry wieght of 50 g./ rn. was produced from theresulting slurry and had a tensile strength of 475 g./mm. and a Finchtensile strength of 130 g./mm. As a cigar wrapper, this tobacco sheetwas very similar to the product of Example 14.

Example illustrates the aspect of the invention of using awater-insoluble acetylated cellulose derivative which was water-solubleprior to being acetylated. T obacco sheets of high resistance todisintegration when moistened can be produced with such water-insolubleacetylated cellulose derivatives whether dissolved in aqueous organicacid as shown in Example 14 or dissolved in organic solvent as shown inExample 15. Other organic solvents suitable for water-insolubleacetylated cellulose derivatives disclosed hereinbefore as beingelfective and desirable binding agents for the production of tobaccosheets include such solvent mixtures, preferably in the indicated weightproportions, as 9 ethylene chloride-1 ethanol, 4 benzene-1 methanol, and10 acetone-1 ethanol.

The foregoing examples are illustrative of the many possible variationsand modifications of the invention. The examples further show that thetobacco sheets of this invention can be utilized to satisfy thedifficult and exacting requirements of good cigar wrapper. Such tobaccosheet can 'be made predominantly of comminuted tobacco which wholly orin part has been ground in essentially a dry form or in the form of aliquid suspension. The tobacco content of such tobacco sheets isgenerally not less than 75% by weight on a dry basis and frequentlyexceeds about 80%. The non-tobacco added components of these tobaccosheets, principally the cellulose derivatives used as the binding agentand, in some cases, cellulosic fiber derived from plants other thantobacco such as softwood pulp, are present in minor proportions usuallynot exceeding 25 by weight of the dry tobacco sheet and frequently lessthan about 20%. The substantially waterinsoluble methylcellulose foundto be effective in producing a cigar wrapper type of tobacco sheet isone having a methoxyl content of at least about 38% by 'weight. As alsodemonstrated by the examples, ash-improving components such as titaniumdioxide and finely divided ceramic fiber are effective when present tothe extent of only a few percent, generally less than 3%, of the weightof the dry tobacco sheet.

What is claimed is:

1. The process of manufacturing a tobacco sheet adapted for smoking andhaving appreciable wet strength which comprises dissolving awater-insoluble acetylated form of an originally water-soluble cellulosederivative in organic solvent which is a mixture selected from the classconsisting of methylene chloride-methanol and ethylene chloride-ethanol,mixing the organic solvent solution with comminuted tobacco so as toyield a slurry containing a minor weight proportion, based on saidtobacco, of said acetylated form of cellulose derivative, casting saidslurry as a thin layer, and drying said layer to produce said tobaccosheet.

2. The process of claim 1 wherein the acetylated form of cellulosederivative is selected from the class consisting of acetylatedmethylcellulose and acetylated hydroxyethylcellulose.

References Cited UNITED STATES PATENTS 3,062,688 11/1962 Detert et a1.131-140 X 3,322,130 5/1967 Panzer et al. 131-17 MELVIN D. REIN, PrimaryExaminer US. Cl. X.R. 131-17 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 49 947 Dated February 24, 1970 Inventor(s) JohnTownend It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 4, "chines, interestingly" should read -chines.Interestingly-; line 30, closed the use of dialdlhyde starch ascrosslinking" should read -U. S. patent Z, 769, 734 that a water-solublebinding--; line 32., "dialdahyde" should read --dialdehyde--;

line 67, "acetice" should read --acetic--.

Column 3, line 36, Column 4, line 21, "water insoluble" should read--water-insoluble-. Column 7, line 54, "consin tobacco fines" shouldread --consin tobacco and tobacco fines- Column 8, line 11,"attractivve" should read --attractive--; line 61, "7. 5%" should read--7. 5%,

Column 9, line 48, "to" should be deleted and "acid," should read -acid.line 75, "thorugh" should read --through--.

Column 10, line 3, "ZOO-meshed snreen. should read --2.00-mesh screen.

SIGNED AND SEMED (SEAL Amt:

WILLIE E. 'SGHUYLER, JR. Gonnissionar of Patents "tobacco product."should read --tobacco product,

FORM PO-IOSO (10-69) USCOMM-DC 60376-P6D n us, covnunzur nmmna ornc: is"o-ass-su

